Structural splitting self plugging pull mandrel blind rivets are designed so that the portion of the T-mandrel which breaks off from the portion held by the riveting tool remains in the tubular rivet body. This is typically accomplished by use of a suitably shaped nosepiece for the rivet tool which engages the head of the tubular rivet body and pushes material around locking rings provided on the T-mandrel adjacent the head of the tubular rivet body. However, if non "fishmouth" shaped nosepieces are used on the T rivet tool or an otherwise improper or worn nosepiece is used, the head of the tubular rivet body is not suitably deformed into the locking rings of the T-mandrel and the T-mandrel subsequently comes free of the tubular rivet body. When this occurs in an automobile body, undesirable rattling caused by the T-mandrel typically results. It should also be appreciated that a failure to properly lock the head of the rivet body to the T-mandrel can also occur when warped materials are fastened, by inattention of the operator to proper installation techniques, and by using rivets assembled at less than or greater than the specified grip range.
Disclosed in U.S. Pat. No. 4,639,174 (Denham et al) is a self plugging blind rivet which includes a progressive reduction in diameter of the plug portion of the mandrel in the direction of the mandrel head. Due to the folding and compressing of the rivet body material at the blind side of the rivet hole, an outward circumferential bulge is provided. The folded material enters into a groove formed by an abrupt reduction in diameter of the plug portion of the mandrel stem. Thus, a secondary locking groove is provided, but it is located outside of the material being fastened and thus requires extra clearance. In addition, such a rivet is complicated and thus difficult and expensive to make.
In U.S. Pat. No. 4,211,145 (Dolch), a blind rivet fabricated out of thermoplastic material and having a sealing ring spaced from the set head is disclosed. The sealing ring has a diameter larger than the tubular rivet and is spaced from the head so as to be disposed within the through holes of the coupled parts and thus to be wedged in place.
Other blind rivets having various locking means of general interest are disclosed in the following U.S. patents: U.S. Pat. No. 4,897,004 (Norton); U.S. Pat. No. 4,897,003 (Bradley et al); U.S. Pat. No. 4,367,994 (Francis et al); and U.S. Pat. No. 4,318,650 (Llauge).